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mdsolar writes "Renewable Energy Access is reporting that a consortium led by researchers at the University of Delaware has achieved 42.8% efficiency with a silicon solar cell. The method uses lower concentration (factor of 20 magnification) than the previous record holder (40.7% efficiency) so that it may have a broader range of applications, since tolerances for pointing the device will be larger. They are now partnering with DuPont to build engineering and manufacturing prototypes. They expect to be in production in 2010. On a roof, such cells would require less than half the surface area to produce the same amount of power as today's standard solar panels, which have an efficiency of about 17%."

I'm interested in solar power as a means of lowering the fossil dependency - but there are other, better means of doing so. The CE manufacturers need to meet them half way and mandate more efficient devices that consume less power and bring back the humble ON/OFF switch that actually did turn off the power. Is it that hard to walk to the TV? And, of course, wind and tidal need to be followed up.

The main problem is the general public. Everybody wants wind power (but not in their back yard) you have to actually change the law and rubbish collection to get them to recycle, and everybody needs to buy the latest and most powerful gadget on the market.

Making a more efficient solar cell is an excellent step, but I'd be more interested in a more *cheap* one so they can be taken up on a mass scale.

The most efficient use of solar power is the water heating system. Solar panels are a distant second for now - as they are very costly for the power they can produce (we assume your house needs heating or hot water). Depending on conditions, wind power might be a cheaper overall choice than solar panels.
But in places like California, solar panels indeed pay for themselves

Peak solar power is around 750W per square meter of installation. With those new panels, you could get - let's say - 1000W per 4 square meters (40 square feet).
Assuming you are going at work using 10kW (14 HP) average for two hours (both ways), and assuming 6 hours a day peak power, and your losses are zero, you need less than 15 square meters (160 square feet).
Now, if you add 50% losses in the recharge system (car and house), you need to double that - 30 square meters, or some 300+ square feet of solar installation, inclined to an angle equal to your location's latitude (equator- flat roof top, Alaska - sharp roof)

Assuming your car has 20 square meters of surface, all of it oriented towards the sun. In Ecuador. With 100% efficient solar panels.
You can get at most 20 HP of power from that. In your real situation, with maybe 5 square meters of surface available in the morning, and lower solar power, and the 40% efficiency solar cells, you get 2HP (or 1.5KW). Does it help? A bit, yes. If your car can load itself all day with energy, and know when she will reach destination, she could bleed the electricity storage battery (and reload it later). This way, you could get 10 square meters of max power, 8 hours a day, and with perfect efficiency in rest (charge, discharge, motor) you get 80 HP hours - or two hours at 40HP. Good enough for a commute... but...
Now, you could buy solar panels at $5000 per kW (and 20 pounds). Assuming double efficiency is treble the price - you need $15,000 per square meter, so you'll pay $150,000 for solar on your car. Is it worth to drop your fuel consumption 50%? Or completely?

It might be so - however, I don't know the costs of a ground-source heat pump. Did any digging recently? Also, you can get hot water at a higher efficiency than electricity from solar power, and the costs of installations are lower to boot. What a solar water heating system can't give you (but a PV panel/ground pump could easily) is cooling

It probably takes a lot more than three years to pay back the investment. A three year payback would be astounding. If that were the case, you could shut down all the existing power plants and run the country just on solar. OK, that's a bit exagerated because solar doesn't make power all the time. Even so, a three year payback would see a dramatic increase in solar use.

The calculation that produces a three year period says that you start saving money after three years. It assumes that you borrow money to buy the panels. After three years, the money you save on electricity is greater than the loan payments. The link below has a graph. You will notice that the savings take a big jump after twenty years. That's when the loan is paid back and you aren't making payments any more. So, using the link's assumptions, the payback on the investment is about twenty years.

My parents live in an area that has lots of wind turbines. A few years ago, many of these were small, high-rpm turbines that were clearly audible from hundreds of meters away. Sitting in the back yard, you always had this droning noise in the background, this could be very annoying.Things did get better when they started replacing the small turbines with fewer, much larger ones. The turbines closest to their house were removed, and the new turbines ran at much lower rpm which means they produce less noise.

As for sticking solar panels onto the turbine blades: this would make the blades heavier and less efficient. Also, you'd have to add slip rings on the root of each blade, and on the main shaft to transfer the power.Slip rings are expensive, heavy and they need maintenance, especially when you're transferring significant amounts of power through them.

That is why the two should be combined... Water-cooled Photovoltaic panels give the best of both worlds: cooler PV panels which are more effective PLUS warm/hot water for heating, hot water or - indirectly - cooling. The technology is out there. It is simple. It works. As to why is is not used that much yet? Good question.

A search on 'water cooled pv' [google.com] gives some interesting documents about experiments done with this combination. Read them and then go and build something like that. My 2 puny 11 watt panels are somewhat to small for this application but anyone who has (plans for) panels on the roof AND a need of warm water does him/herself a disservice by not looking in to this IMnsHO...

"The CE manufacturers need to meet them half way and mandate more efficient devices that consume less power and bring back the humble ON/OFF switch that actually did turn off the power."

I recently had a new lady move in with me... and she insisted on actually unplugging things like my stereo when we were not using it. I was skeptical about the benefits of this tactic to save electricity, but being a curious person I was willing to humor her.

By unplugging all of my electronic devices (there are many of them) when not in use we saved around $30 U.S. a month. Where was all that energy going? Not sure.

If you are the type of person that has electronics in every room give it a try for yourself. Even if you don't care about being 'green' you will likely see a difference in your energy bill. Either way you win.

This is exactly how I treat my HOA. I do what ever I want and let them come and fine me for it latter. Really, my HOA is just a way for some Assholes with too much time on there hands to make money off everyone else. hmm, remind you of anyone?? Like they required that I have my house painted by company X, well, I went with company Y, payed a fine for it but still saved my money, they did a better job then my neighbors got plus I feel better not hiring a company that gives kickbacks to my HOA.

Seeing a car's power rated in terms of horsepower has always seemed somewhat excessive to me. For a long time, people used a single horse[1] to get around. They were quite slow for long distances, but could achieve something close to the legal speed limit for built-up areas. Since we're playing with absolutely ideal numbers, let's try another one; the car has zero mass.

According to Wikipedia, the Sun produces approximately 1KW of energy per square metre. Your 20 square metre car then has a 20kW energy output (around 27hp). How fast can this accelerate a human? Assume for now that a human weighs around 100Kg (most people weigh less, so this includes a small luggage allowance as well). One Watt is one Newton per second, and one Newton is the amount of energy required to accelerate one kilogram at one metre per second per second. Your 20 kW car can accelerate a 100kg person at 20,000 / 100 = 200 meters per second, per second. Since this is roughly 20g, you would probably not want to do that very often.

Now we have some absolute upper bounds on optimality, let's stray back slightly towards feasibility. At 40% efficiency, you get 80m/s/s. Still not bad. For reference, 0-60mph in five seconds requires just over five meters per second per second of acceleration. Of course, we're still assuming equatorial sunlight. Dropping the solar energy down to a more reasonable 50% gives us 40m/s/s. Our car still weighs nothing, however, so let's run this the other way; if we want 0-60 in 5 seconds, how much can our car weigh? The answer comes out at 700kg (800kg including passenger), which is not too bad; a quick google indicates that this is about half the mass of an average car.

It seems that a totally solar car is not completely beyond the realms of feasibility with current technology, but it will probably not be commercially viable for some time. For one thing, you're going to need a battery for when it's cloudy or night, which will drive up the mass very quickly.

[1] The original definition of a horsepower was for mine ponies, so a cart horse probably provided a few horsepower.

As per the summary, solar cells are 17% efficient. The efficiency of a heat pump will vary quite a bit depending on working temperatures, but the compressor motor will doubtfully be more than about 80% efficient (electrically). So overall, at best, 14% of the sunlight makes it into the hot water.

Compare to direct solar heating, where damn near 100% of the energy you absorb gets transferred to the water. After all, the desired end product is heat, and it's trivial to convert 100% of any energy form into heat if you're patient enough.=Smidge=

Joking aside, the best thing you can do for the energy usage of your home is ensure it is properly insulated and buy the quality efficient heating/air units. You can take it further by buying those new florescent light bulbs that are only around 14 watts, and having your computers hibernate during the day and night when you're not using them. You could see your power bill cut in half if you do all that.

I looked into this recently. Installing a ground based heat pump instead of a regular air conditioner would have been around $6K (instead of $2K for the AC). Note that this was for an old style 12 SEER AC unit that's no longer available against a 25+ SEER heat pump (get added bonus of generating heat). AC units have almost doubled in cost, and now are about $4500 installed (new US regulations require higher SEER units).

Why didn't I get the ground based system? Because when it's over 100 F and your main AC unit dies, I couldn't wait for the ground based unit installation taking over a week. I will plan for one at my next house though.

By unplugging all of my electronic devices (there are many of them) when not in use we saved around $30 U.S. a month. Where was all that energy going? Not sure.

It goes to heat production, mostly. However I prefer a step forward rather than taking a step back by having to turn everything off. It is possible to make equipment have a minimal power consumption on standby, by only running a small circuit that looks for the "On" button being pressed on the device. A lot depend on how you power this circuit... a transformer is a notoriously bad way of doing it.
Some equipment behaves nicely on standby. Use a Wattmeter to check how much your stuff actually consumes in standby mode; you'd be surprised how little some things consume when idle, and there is little use in unplugging these completely. You might also be surprised at the large amount of power drawn by plug in transformers (The "wall warts"). Removing these when you are not using them saves a lot.

Another good way to save without sacrificing convenience, is to use a "master-slave" power block with your computer. I have a lot of inefficient transformer power supplies next to the computer, for printers, routers, LCDs, speakers, etc. I installed a "master-slave" system, that will automatically switch off all this rubbish when the computer is switched off. The power draw of this system when idle is minimal compared to those transformers, and you don't have to switch off every individual piece of equipment either,

Most of the cost today is the module. Systems go (net) for 4-5$/Watt.More efficient cells (and modules) mean less installation costs. For the future, it will be important since cell and module prices will go down.

Today, in California, if you take a system lifetime of 25 years, the kWh equivalent "price" is about 25-30cent.

System price decrease is expected to be 5-10% yearly for the next 5-10 years at least. This means that very soon the PV power will be cheaper than the one sold by the utility.

PV systems are perfect for distributed energy: a centralized power plant is not really cheaper or more efficient than a 5kW roof installation. And the energy transport kills the small margin that you had in favour of the big thing. That is why most utilities are not hot about PV: it is against their business model.

For the moment, it is not cheap to get "disconnected" from the grid. Therefore, a mix of PV and other electricity is necessary. PV has a nice peak at max. consumption peak. However, the evening consumption must be covered otherwise. Wind, biomass, ocean waves, geothermal, whatever.

PV in order to charge e-cars is OK today already. A car that uses 10 liter to do 100km, at a 20kW mean power, is using 20kWh energy for 10 liter gas, at 1$/liter it would be 50 cent/kWh. Make the calculation with your local gas price/gallon and you see that, even today, it is competitive. And cleaner. Only e-cars are not yet developed/deployed as they need to be.

About Solar-thermal energy for cold- it works for mid-big sized equipments, it is cheaper and especially more reliable than electricity... PV supporting electrical AC is still a bit more expensive but both run a nice race.

Ah, the typical guy asks about energy payback times: depending on technology, after 1-4 years your system has produced the energy needed to make it. Longer times belong to PV prehistory and to right-wing-thinktank analysis.

> On a roof, such cells would require less than half the surface area to> produce the same amount of power as today's standard solar panels,> which have an efficiency of about 17%."

The article being quoted clearly states that these cells require concentrated sunlight -- this is true of all thin-film high-TSE cells. So basically you can't mount them on the roof, you'll get no power at all.

Further, most solar panels get about 11% efficiency. There are ones that get into the 15-17% range, but these are much more expensive and see considerably less use as a result.

These new cells will be very useful for large-scale energy developments, like large solar farms in the desert. They are completely useless for rooftop deployment.

1) Ice ages are somewhat random events so saying 10,000 years we will be in an ice age is silly it may have already happened or yet to start. Looking back several million years ices ages have no where near the consistency as the seasons. They don't all get as cold they don't last the same amount of time and they don't occur on a regular basis.

2) Both sides are trying to muddy the waters. You don't hear "Everything will be fine" and you don't hear "We are all going to die" because there is some give and take with every publication.

3) Some people think we can't change the climate. But looking at the "Dust Bowl" in the US and "urban heat island effect" it's clear we can alter the local climate in significant ways.

4) It's generally accepted that increasing CO2 increases global temperature up to a point but we don't know what all the effects of increased global temperature are going to be. It's probably going to be expensive / destructive for low lieing costal cities but most of the temperature increase is going to occur in the north which might increase economic activity enough to help offset some of the damage.

IMO: I suspect in the long term (1000+ years) we will carefully control the worlds climate. Over the realy long term 10,000 - 1,000,000 years we may decide to alter the earths orbit and fine craft our heat output to deal with the amount of energy we are generating, but right now we don't have the tools or experience to deal with significant climate change. As with most significant changes large numbers of people are going to die and then the world will adjust and move on. It's not the end of the world just the end of our world as we know it.

Some VW/Audi models have a "solar sunroof", which is nothing more than a small solar panel mounted on the sunroof. It is used mainly to produce energy to keep the AC fans working even when the engine is shut off (when there's sunlight, at least), to keep the interior of the car cooler than it would normally be if it were parked in the sun. Since the car interior is, on average, 20 degrees celsius cooler, the AC will have a much easier task of cooling the cabin to the desired value, thus saving a little bit of fuel. Pretty neat.

I saw a Nova (IIRC) where Germany is subsidising individuals to put up solar cells. Farmers are covering entire fields with them. They have a contract so that they are garunteed to recoup expenses and make a profit.

Germany lines all of its freeways w/ solar cells. That is making good use of otherwise wasted space.

I hope other countries (the US included) take some lessons from the Germans.

In fact, roof top concentrators look quite practical: http://www.technologyreview.com/Energy/18718/ [technologyreview.com]. I wish the original article had given a diagram of how their system is laidout, but it definitely mentioned rooftop use.

You won't be all that competitive is you are producing 11% efficient solar today. I think perhaps you are thinking that most solar panels already sold have a lower efficiency. One company is selling at $3.00/watt for lower efficency panels as compared with $4.20/watt for most. You have to compete on price to offset the higher installation costs of lower efficeincy panels. --Solar power you can afford: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html [blogspot.com]

A rather one-sided presentation, I might add, but since you concede that this has already been countered by pointing out Albright's poor science and publishing his own website calling his boss's work a "myth", I don't need to get into details.

The same happened with two scientists in a Dutch government-run climatological research institute.

Really? Who? The only one I've heard of is Tennekes, and as far as I've ever been able to determine, he was not fired — he simply retired. He certainly has said nothing to the contrary himself; all the claims about him being fired can be traced back to an off-hand claim by Lindzen.

Who else were you thinking of?

That goes for both sides of the table, however most politicians, scientists and activists have far more to gain by a "let's impose controls" attitude than with a "nothing to see here, move along" attitude, the global warming camp is far more influential than the sceptics camp.

I am trying to imagine what scientists have to gain by imposing economic caps on carbon. I really hope you aren't going to drag up the "they can't get grant money otherwise" claim.

The current rate of warming is nothing exceptional, and might even be just a ripple in the trend.

On the contrary, there is no evidence for any rate of change as large as present, other than the abrupt D-O events associated with a collapse/restart of the thermohaline circulation.

The past has seen increases in temperature of higher rates and over a larger range.

You are obfuscating the issue. Remember that my point was this: the rate of warming is larger than the natural rate of cooling into an ice age. This is true. There have been other events, not associated with the ice age cycle, which have shown a rapid cooling. But this is irrelevant to either my point or yours (which was that we need the warming to offset imminent cooling). It's irrelevant because there is no such imminent cooling. Ironically, global warming itself is the only thing that could set off that kind of rapid cooling via a THC collapse right now, and even if it did, the amount of warming needed to trigger such a collapse would likely outweigh the resulting cooling itself.

That's also the pattern to most ice ages (and we're at the peak following a small one of a couple 100 years ago):

We are in an interglacial period, but it is dishonest to claim that we are at the "peak" of one, implying that it's all cooling from here on out; there is no evidence of this.

a slow decline in temperature, followed by a sharp ramp upwards.

The "sharp ramp upwards" during a deglaciation is still significantly slower than the current rate of warming, and is also irrelevant to your claims about imminent cooling.

Warming and cooling are natural trends, on which we have some (small influence).

The influence may be "small" compared to the total change involved in the ice age cycle, but that doesn't mean that the resulting impacts are negligible in any absolute sense.

We should be worried about the warming trend, but not exaggerate our supposed influence.

Nor should we minimize our actual influence.

Thart's like worrying about a small wave, while the normal tide raises and drops the water level by several meters.

That's also a dishonest analogy, since you are choosing as a basis for comparison something (a small wave) which demonstrably has no impact to society as a whole. You cannot demonstrate the same about current climate change. Furthermore, the fact that there have been large climate changes in the past is a red herring; sure, the Cretaceous was much warmer than today, but that doesn't mean that we'd prefer to live in that climate.

We have seen nothing yet.

Of course this is false; we have seen a warming trend, which appears inexplicable in terms o

In such a setup, such as for a off-grid solar power house the cost benefits of using thermal solar for heating the water outweighs the loss of flexibility. Panels for solar water heating are generally at least an order of magnitude cheaper than solar electric panels. You simply oversize your water tank(and insulate it well) to last through a cloudy day/night.

Along with that getting specialized home appliances can be cost effective; special extreme efficiency 24 volt DC refridgerator, for example. Reducing your install by 1 panel can save several thousand dollars easy.

Not only is the theoretical maximum efficiency of blackbody air to water (with solar deflectors added in) max out to around 60%, so not much improvement needed to be equal. (since this 40%+ efficiency needs deflector as well)

being in the process of doing a solar water heater myself, regardless the path you choose, you still have to run a pump, to even get close to a 14% solar direct to water heater efficiency.

IE you can place the storage tank above the heater, and pull your fresh water through the heater, and storage tank, allowing some thermal circulation, then your incoming water pressure to move things, but you surely won't be anywhere near even the 14% efficiency of a 14% EF PV panel (you will be much, much cheaper though)

in my system I have got a 65Watt 12VDC water pump circulating pump, and on order, 3*15Watt PV solar panels, a cheap charge controller [suburbia.com.au] and a solar panel. I am re-using my old water heater, and ordering a on-demand water heater to make up for only having room for a 20 gallon tank, when a 100 Gallon tank would be better sized.

even 100% DIY, many free parts, and Arizona sun. I am still going to be over $1000, to save maybe $200 a year in grid electric.

given an estimated total build cost of $1.60/watt [wikipedia.org], that's roughly equivalent to nuclear [uic.com.au], but without all of the ongoing costs of large security forces, fuel cycles, decommissioning, and all of the nasty waste left over. let's not forget that uranium is getting more expensive and the spent fuel is piling up.

Now, i'm not anti-nuclear, in fact i think we should be building breeders as fast as wen can, but to discount wind, which is economically similar to nuclear in build cost per watt, is cheaper to maintain, and doesn't have a lot of the nasty side effects because of someone as subjective as "it's ugly".... seems silly to me>

how pretty are a bunch more nuclear reactors all over the place?

how much beautiful habitat will your kids miss out on because there's a power plant there?

how much land will be restricted from your babies eyes because of the countless acres around the waste storage facility that are cordoned off for national security?

wind turbines can be put right where power is needed if the location has a steady breeze, the're high enough off the ground that the land underneath is still usable for farming or.... whatever.

it's not nearly as ugly as it used to be, is it really worth discounting?

Actually, there's another issue with solar hot-water systems: home owners associations. In my particular case, I can't put such a system on the preferred side of the roof because it'd be visible from the street (my house faces SSW). There's also the issue of performance, although I've not looked into this in the past 8 years so I'm not up on any improvements.

Vegetation varies greatly. I've seen figures as high as 10% for high yield plants. Just to guess, a fast growing healthy tree might be 1%, an old hardwood 0.1% or less. Something like a bristlecone pine would be very poor, indeed. Where I live (southern New Hampshire) the growing season is only 5 months, so more than half the year is completely lost.